Remove java.util.Optional from View contract

spring-web-reactive/src/main/java/org/springframework/web/reactive/result/view/AbstractView.java

@@ -114,15 +114,15 @@ public abstract class AbstractView implements View, ApplicationContextAware {
 	 * @return
 	 */
 	@Override
-	public Flux<DataBuffer> render(HandlerResult result, Optional<MediaType> contentType,
+	public Flux<DataBuffer> render(HandlerResult result, MediaType contentType,
 			ServerWebExchange exchange) {
 
 		if (logger.isTraceEnabled()) {
 			logger.trace("Rendering view with model " + result.getModel());
 		}
 
-		if (contentType.isPresent()) {
-			exchange.getResponse().getHeaders().setContentType(contentType.get());
+		if (contentType != null) {
+			exchange.getResponse().getHeaders().setContentType(contentType);
 		}
 
 		Map<String, Object> mergedModel = getModelAttributes(result, exchange);

spring-web-reactive/src/main/java/org/springframework/web/reactive/result/view/View.java

@@ -55,6 +55,6 @@ public interface View {
 	 * @param exchange the current exchange
 	 * @return the output stream
 	 */
-	Flux<DataBuffer> render(HandlerResult result, Optional<MediaType> contentType, ServerWebExchange exchange);
+	Flux<DataBuffer> render(HandlerResult result, MediaType contentType, ServerWebExchange exchange);
 
 }

spring-web-reactive/src/main/java/org/springframework/web/reactive/result/view/ViewResolverResultHandler.java

@@ -121,7 +121,7 @@ public class ViewResolverResultHandler implements HandlerResultHandler, Ordered
 
 		return returnValueMono.then(returnValue -> {
 			if (returnValue instanceof View) {
-				Flux<DataBuffer> body = ((View) returnValue).render(result, Optional.empty(), exchange);
+				Flux<DataBuffer> body = ((View) returnValue).render(result, null, exchange);
 				return exchange.getResponse().setBody(body);
 			}
 			else if (returnValue instanceof CharSequence) {
@@ -131,7 +131,7 @@ public class ViewResolverResultHandler implements HandlerResultHandler, Ordered
 						.concatMap(resolver -> resolver.resolveViewName(viewName, locale))
 						.next()
 						.then(view -> {
-							Flux<DataBuffer> body = view.render(result, Optional.empty(), exchange);
+							Flux<DataBuffer> body = view.render(result, null, exchange);
 							return exchange.getResponse().setBody(body);
 						});
 			}

spring-web-reactive/src/test/java/org/springframework/web/reactive/result/view/ViewResolverResultHandlerTests.java

@@ -277,9 +277,7 @@ public class ViewResolverResultHandlerTests {
 		}
 
 		@Override
-		public Flux<DataBuffer> render(HandlerResult result, Optional<MediaType> contentType,
-				ServerWebExchange exchange) {
-
+		public Flux<DataBuffer> render(HandlerResult result, MediaType mediaType, ServerWebExchange exchange) {
 			String value = this.name + ": " + result.getModel().toString();
 			assertNotNull(value);
 			return Flux.just(asDataBuffer(value));

spring-web-reactive/src/test/java/org/springframework/web/reactive/result/view/freemarker/FreeMarkerViewTests.java

@@ -127,7 +127,7 @@ public class FreeMarkerViewTests {
 		ModelMap model = new ExtendedModelMap();
 		model.addAttribute("hello", "hi FreeMarker");
 		HandlerResult result = new HandlerResult(new Object(), "", ResolvableType.NONE, model);
-		Flux<DataBuffer> flux = view.render(result, Optional.empty(), this.exchange);
+		Flux<DataBuffer> flux = view.render(result, null, this.exchange);
 
 		TestSubscriber<DataBuffer> subscriber = new TestSubscriber<>();
 		subscriber.bindTo(flux).assertValuesWith(dataBuffer ->